The invention relates generally to optical coupling.
In many integrated photonic advanced processing applications, orthogonally coupling of light from different components remains a significant challenge. For example, in some embodiments vertical cavity surface emitting lasers (VCSELs) embedded in flat multi-chip modules (MCMs) need to be coupled to a wave guide, and in other embodiments the light needs to be coupled from wave guides fabricated on a flat surface to an orthogonal direction through a supporting substrate.
One technique for orthogonal coupling is to position a prism with surfaces adjacent the emitting and receiving elements. Conventional prisms are expensive to fabricate due to the small size (a 2 millimeter by 2 millimeter prism can be fabricated for about $100.00, for example). Additionally, conventional prisms are difficult to handle especially when positioning and aligning to the two elements.
Another technique for orthogonal coupling by machining a forty-five degree mirror into the end of a wave guide, for example, can be difficult to achieve, even in multi-mode wave guide embodiments wherein the wave guides thicknesses are on the order of about 20 microns to about 50 microns, and can be even more difficult to achieve in single mode wave guide embodiments wherein the thickness are typically about 2 microns to about 6 microns. Mirror machining becomes unstable due to the geometrical dimensions.
Still another technique for orthogonal coupling is using a flexible wave guide loop wherein the wave guide extends substantially straight from the substrate and gradually curves downward until the remainder of the wave guide is flat on the surface of the substrate. This technique is not compatible with embodiments wherein planar technologies must be used.
It would therefore be desirable to provide a structure for coupling of light from a wave guide to an embedded light element.
Briefly, in accordance with one embodiment of the present invention, an optical coupler comprises a fiber optic prism (FOP) comprising first, second, and third side surfaces, the FOP being adapted to receive light through the first side surface, reflect the received light from the third side surface, and transmit the reflected light through the second side surface.
In accordance with another embodiment of the present invention, an optical coupling arrangement comprises: a substrate including a light element; a wave guide overlying the substrate; and a fiber optic prism (FOP) comprising first, second, and third side surfaces, the FOP being adapted to receive light through the first side surface, reflect the received light from the third side surface, and transmit the reflected light through the second side surface, the FOP being situated such that one of the first and second side surfaces is adjacent the light element and the other of the first and second side surfaces is adjacent the wave guide.